Process of making tetra-alkyl lead



Aug. 24, 1937. M. G. AMlcK Er AL PROCESS OF MAKING TETBAALKYL LEAD Filed- 001'.. 27, 1934 iY I'I NN Y A Patented Aug. 24, 1937 UNITED STATES PATENT OFFICE PROCESS OF MAKING TETRA-ALK LEAD Application October 2,7, 1934, Serial No. 750,322

4 Claims.

and ability to operate under raised temperatures and pressures without the necessity of interrupting operations to cool the charge and reduce the pressure to prevent the same becoming excessive, and ability to work with large charges, it is highly satisfactory to work with an apparatus in closed system. 'I'his comprises an autoclave, a condenser, and a storage tank in circuit. In operation, ethyl chloride evaporating from the reaction mass is condensed and returned to the autoclave by way of the storage tank. Heat is thus removed from the reaction mass, and by controlled return of the cooled condensed ethyl chloride to the autoclave. the temperatures and pressures are readily controlled. The cooling eiect so eectively supplements the jacket cooling of the autoclave that large charges can be used. That is, the diillculty that it is not feasible, because of diilculties in heat transfer, to use large charges where only jacket cooling of the autoclave must be relied upon, is overcome. Indeed, with cooling by the evaporation of ethyl chloride it becomes unnecessary to use refrigerated cooling medium in the autoclave jacket, water at normal temperature being adequate; and this eliminates high refrigeration expense.

When practicing the above method commercially, and hence, for economy and so forth, with ethyl chloride in but relatively small excess above that theoretically required for reaction with the alloy, say an excess of but 50 to 100% it is highly important to ensure that non-condensable gases shall not vapor lock the system and/or build up undue pressures. These gases, e. g. ethylene, ethane, butane and so forth are formed during the reaction and are non-condensable under' com-'- mercially practicable cooling conditions. While when a large excess of ethyl chloride is present the ethyl chloride may sufficiently dissolve the gases, it is preferable not to rely on this when but a relatively small excess of ethyl chloride is used.

One object of the present invention is to provide a method having the advantageous features above outlined. A further object is to provide a method embodying provisions against vapor lock and excessive pressures, automatic control, and various other advantageous features. A further object is to provide an apparatus for the practice of the indicated method. Further objects will appear hereinafter.

These objects are accomplished as follows, reference being made to the accompanying drawing in which: Figure 1 isa conventional perspective view of an apparatus for the practice of the method, and embodying the invention in its apparatus aspects: and Figure 2 is a broken out vertical diametrical cross sectional view of one of the condenser tubes and its volume restrictor, to a somewhat larger scale than Figure 1. Referring now to the drawing:-

'Ihe illustrated assembly comprises the autoclave i, condenser 2 of a shell-and-tube type for condensation of the ethyl chloride vapor from the autoclave, and ethyl chloride supply tank 3, all connectedin closed circuit by the pipes 4, 5 and 6. In operation, aweighed amount of lead-monosodium alloy is introduced into the autoclave through the feed device l, the valve 1* closed, and the agitator (not shown) in the autoclave started. The tank 3 having been supplied with ethyl chloride, ethyl chloride is then allowed to flow by gravity and preferably continuously, in'to the autoclave, the valve 6 being adjusted to regulate the' rate of feed and the exact amount fed being indicated by the dial I'll of the scale il hereafter referred to. This eliminates the necessity of adding an initial amount oi' ethyl chloride to the autoclave and then awaiting evidence of reaction starting, before feeding the remaining ethyl chloride. Considerable time is saved during the reaction cycle due to the ability to feed ethyl chloride rapidly and continuously. As soon as the reaction between the ethyl chloride and the alloy commences, heat is generated in the reacting mass, rapidly heating up the ethyl chloride which vaporizes readily and absorbs the heat of reaction. The ethyl chloride is condensed, returned to the autoclave by way of the tank 3, revaporized to remove more heat, and so on until completion of the reaction.

Special provisions are made to ensure that there shall be no vapor lock. In the present instance, the ethyl chloride is given such high velocity through the condenser that any non-condensable gases are carried through the condenser and into the tank 3. This latter is of such capacity as to provide for collection of the gases without undue increase in pressure, or if it becomes advisable, the gases may be vented through the valve 8 (as to any suitable recovery system).

We have found that the vapor velocities through the condenser should be those above which turbulent flow is obtained. This occurs above a Reynolds number of 2100 in consistent units.

5 To attain this end in the illustrated condenser 2 each vapor pipe 9 (Fig. 2) is provided with a volume restn'ctor shown as a tube III hung from the cross pin I I. In this way the cooling surface of the tube 9 is not diminished, but the effective l0 internal diameter of the tube is reduced with consequent increased vapor velocity. For instance, a tube of 1 inch outside diameter and a wall thickness of .065 inch may be provided with a volume restrictor 3A inch in diameter. Obviously the tubes 9 should be of suiiicient length and cooling surface to provide for condensation of the ethyl chloride in its travel, despite the high velocity. We have found a condenser of 73 tubes of about 98 inches in length generally entirely adequate.

Automatic control of the pressure in the system, and hence in the autoclave, is provided in the present instance by the condenser 2 and its connections. The flow of cooling medium through the condenser is automatically controlled by a pressure-type diaphragm-operated valve I2 of the usual standard type and embodying a valve proper, a diaphragm for operating the valve and responsive to the pressure in the condenser, and means for setting the device for operation at desired pressure. The valve controls the flow of cooling medium supplied to the condenser through the valve I2 and flowing from the condenser through the pipe I3. The cooling medium should preferably be a substance (such as kerosene, and the like) that is inert to the reacting components.

With the pressure valve I2 set for maximum.

desired pressure in the autoclave, as the pressure in the autoclave and hence in the condenser tends to rise above this, the valve automatically opens wider and more cooling medium iiows through the condenser, thus cooling the ethyl chloride at'a greater rate and causing the pressure in the cycle to drop. This tends to close the valve and limitthe flow of cooling medium to the condenser, and so on. In this way an equilibrium is attained between the pressure in the system and the temperature within the autoclave and the reaction mass. Desirably, the temperature of the ethyl chloride liquid condensate is held below that corresponding to the pressure desired in the` autoclave reaction, andas this relation is constantly and automatically maintained, there results a close control'of the reaction and an ability to maintain the reaction at highest economy.

The autoclave is suitably jacketed for flow of 'a cooling medium as conventionally indicated at M. Water at normal temperature is ample for the slight amount of cooling required in the auto- 'clave jacket, The cooling medium for the condenser is supplied and withdrawn through the headers I5 and I6. Conveniently, the supply tank 3 is supported upon a scale I1 having the weight-indicating'l dial Il. As will be understood, the exibility of the connected piping permits proper. operation of the scale, a proper tare being readily determined.

The pipe 6 is valved at 6 for the controlled and restricted return'of the ethyl chloride to the autoclave, /the rate of return beingthat to give the -particular degree of cooling by the ethyl chloride, and the particular reaction conditions, desired in any particular case, as will be understood by those skilled in the art. As is evident, the rate of return may be different from, e. g. less than, the rate at which the ethyl chloride is delivered from the condenser.

As here shown, the vapor pipe 4 is connected to the autoclave by way o1' the feeder l. To the pipe I is connected the pipe I8, for venting the autoclave as to any suitable recovery system. The pipes 4 and I8 are valved at 4 and I8a as shown. I l0 In operation, as soon as a drop in pressure in the system indicates the end of the ethylation reaction, the valve E is closed and the reaction mass cookcd" for a given time by means of hot water introduced into the autoclave jacket, thus 15 completing the retion. When the reaction is completed, the excess ethyl chloride vapor, together with such non-condensable hydrocarbon gases as butane, ethane, and so forth, as may be present in the autoclave, is removed from the au- 2U toclave, being vented, say, into an ethyl chloride recovery system. The recovered ethyl chloride is pumped back into the tank 3 through the pipe I9, for a future reaction cycle.

As will be understood, the details of the perl5 formance will vary with the particular alkyl halide used and similar factors. When working with ethyl chloride and lead-mono-sodium alloy it has been found desirable to hold the pressure to an amount corresponding to a reaction temperature 5U between 60 to '70 C., the pressure for this temperature being about 60-'10 pounds per square inch gauge. The general process of reacting alkyl halide and lead sodium alloy for the production of alkylated halide is, of course, Well understood 35 and in its general broad aspects does not form a major feature of the present invention.

It will be noted that in the present preferred operation, in which the supply of ethyl chloride is initially placed in the tank 3, and from the 40 start of operations is fed in controlled and restricted amount to the autoclave, full advantage is taken of the. equalization of pressure between the tank and the autoclave. 'I'hat is, the ethyl chloride when rst fed to the autoclave, as well 45 as during the course of the procedure, may be fed under pressure, without the necessity of vapplying to the 'ethyl chloride the pressure of an extraneous agent, e. g. nitrogen under pressure. It will be evident thatI this principle of operation is of 50 general application in that it-may be used to advantage .whether or not the equalizing connection from the autoclave to the supply container includes a condenser or is merely a connecting piping. l 55 While particular reference has been made to lead tetra ethyl, it will be understood that the invention is applicable in connection with any of the analogous compounds of lead with alkyl radlcals, or analogous metals, such as tin, etc. with 60 corresponding alkyl radicals. It is particularly applicable to such compounds in which each alkyl group contains from one to four carbon atoms. Also, while the invention is more particularly described in connection with ethyl chloride, 'it is 65 of course applicable .with other hydrocarbon halides.

It is apparent that many widely diierent embodiments of this invention may be made without departing from the spirit and scope thereof and. 70 therefore, it -is nctvintended to be limited except as indicated in theappended claims.

What 'is claimed is:

1. In the art of makingtetra ethyl lead by reaction upon lead-sodium alloy with ethyl chloride, 75

apen-112 the process which comprises: reacting low-sodiuml the ethyl chloride, condensing ethyl chloride val circuit.

2. In the art of making tetra ethyl lead by reaction upon lead-sodium alloy with ethyl chloride, the process which comprises: reacting leadsodium `alloy with ethyl chloride, under pressure and at a temperature above the normal boiling point ofthe ethyl chloride, condensing ethyl chioride vapors evolved from the reaction mass, storing the ethyl chloride condensate, and feeding ethyl chloride from storage to the reaction mass,

while automatically controlling the cooling `effected in the condenser responsive Vto, the pressure in the circuit, and also so controlling and restricting said feed as to produce the cooling effect required to constantly hold the reaction at optimum so reaction temperature, said reaction, condensation,

storage and feeding being performed in closed circuit, and meanwhile circulating the ethyl chloride with suillcient velocity toensure the carrying of non-condensable undissolved gases through the condensing equipment and into the storage,

thus preventing vapor lock.

3. In the art of making tetra ethyl lead by reaction upon lead-sodium alloy with ethyl 'chloride, the process which comprises: reacting leadsodium alloy with ethyl chloride, under pressure rasant Nq. 2,091,112.

HAMON lc. AMICK, ET( AL.

and at a temperature above the normal boiling point of the ethyl chloride, condensing ethyl chloride vapors evolved from the reaction mass, storing the ethyl chloride condensate, and feeding ethyl chloride from storage tothe reaction mass, while automatically controlling the cooling effected in the condenser responsive to Vthe pressure in the circuit, and also so controlling and p restricting said` feed as to produce the cooling effect required to constantly hold the reaction at optimum reaction temperature, said reaction, condensation, storage and feeding being performed in closed circuit; and meanwhile circulating the ethyl chloride at a velocity above which turbulent low is obtained thus 'to ensure the carrying of non-condensable undissolved gases through the condensing equipment and into the storage, thus preventing vapor lock.

4. In the art of making tetra ethyl lead by reaction upon lead-mono-sodium alloy with ethyl chloride under pressure and at a temperature above the normal boiling point of the ethyl chloride: providing a body of ethyl chloride separate from the reaction mass and initially supplying the ethyl chloride to the reaction mass therefrom in limited and controlled amount, vaporizing a portion of the ethyl chloride from the reaction mass, condensing the vapors, adding the condensate to the said body of ethyl chloride, and feeding the ethyl chloride mixture to the reaction mass at a restricted rate so controlled as to produce the cooling effect required to constantly hold the reaction at optimum reaction temperature while maintaining the body of ethyl chloride and the reaction vessel at substantial pressure CERTIFICATE 0F ceRRcTIoN.

August 2u. 1957.

1t is hereby certified that error appears inthe printed specification of' the above numbered patent requiring correction as follows.: :Page 5 first Vcolumn, line 1 claim l, for the word low-sodium" read lead-sodium; and

that the said Letters Patent should be read with this correction therein l 4that" the same may conform tothe record ofthe case in the Patent Off ice.

Sign and Sealed this 25th day of January, A. D. i958.

(seal),

Henry Van infedele, Acting Commissioner of' Patente.

apen-112 the process which comprises: reacting low-sodiuml the ethyl chloride, condensing ethyl chloride va- 5 pors evolved from the reaction mass, storing the ethyl chloride condensate, and feeding ethyl chloride from storage to the reaction mass, while automatically controlling the cooling effected in the condenser responsive to the pressure in the l circuit, and also so `controlling and restricting said feed as to produce the-cooling eifect required toI constantly hold the reaction at optimum reactiontemperature, said reaction, condensation, storage and feeding'being performed in closed l circuit.

2. In the art of making tetra ethyl lead by reaction upon lead-sodium alloy with ethyl chloride, the process which comprises: reacting leadsodium `alloy with ethyl chloride, under pressure and at a temperature above the normal boiling point ofthe ethyl chloride, condensing ethyl chioride vapors evolved from the reaction mass, storing the ethyl chloride condensate, and feeding ethyl chloride from storage to the reaction mass,

while automatically controlling the cooling `effected in the condenser responsive Vto, the pressure in the circuit, and also so controlling and restricting said feed as to produce the cooling effect required to constantly hold the reaction at optimum so reaction temperature, said reaction, condensation, storage and feeding being performed in closed circuit, and meanwhile circulating the ethyl chloride with suillcient velocity toensure the carrying of non-condensable undissoived gases through the condensing equipment and into the storage,

thus preventing vapor lock.

3. In the art of making tetra ethyl lead by resodium alloy with ethyl chloride, under pressure rasant Nq. 2,091,112.

HAMON lc. AMICK, ET( AIL.

and at a temperature above the normal boiling point of the ethyl chloride, condensing ethyl chloride vapors evolved from the reaction mass, storing the ethyl chloride condensate, and feeding ethyl chloride from storage tothe reaction mass, while automatically controlling the cooling effected in the condenser responsive to Vthe presp restricting said` feed as to produce the cooling effect required to constantly hold the reaction at optimum reaction temperature, said reaction, condensation, storage and feeding being performed in closed circuit; and meanwhile circulating the ethyl chloride at a velocity above which turbulent ow is obtained thus 'to ensure the carrying of non-condensable undissolved gases through the condensing equipment and into the storage, thus preventing vapor lock.

4. In the art of making tetra ethyl lead by reaction upon lead-mono-sodium alloy with ethyl chloride under pressure and at a temperature above the normal boiling point of the ethyl chloride: providing a body of ethyl chloride separate from the reaction mass and initially supplying the ethyl chloride to the reaction mass therefrom in limited and controlled amount, vaporizing a portion of the ethyl chloride from the reaction mass, condensing the vapors, adding the condensate to the said body of ethyl chloride, and feeding the ethyl chloride mixture to the reaction mass at a restricted rate so controlled as to produce the cooling effect required to constantly hold the reaction at optimum reaction temperature while maintaining the body of ethyl chloride and the reaction vessel at substantial pressure CERTIFICATE 0F ceRRcTIoN.

August 2u. 1957.

1t is hereby certified that error appears inthe printed specification of' the above numbered patent requiring correction as follows.: :Page 5 first Vcolumn, line 1 claim l, for the word low-sodium" read lead-sodium; and

that the said Letters Patent should be read with this correction therein l 4that" the same may conform tothe record ofthe case in the Patent Off ice.

Signed and sealed this 25th day of January, ,A D. i958 (seal),

Henry Van infedele, Acting Commissioner of' Patente. 

